1. Field of the Invention
This invention relates to valve actuators, and more particularly to a safety shut off mechanism for valve actuators.
2. Description of the Prior Art
The art generally recognizes a wide variety of and various applications for motor driven valves. The motor mechanism for driving a valve usually comprises an electric, pneumatic or hydraulic prime mover which is coupled to an output shaft that is mounted for rotation or reciprocation, by way of an intermediate mechanism, such as a gear train. U.S. Pat. No. 3,572,163, of Malcolm D. Clark, issued Mar. 23, 1971, discloses electrically energized actuators for both light and heavy-duty applications. Each of the actuators disclosed by Malcolm D. Clark are of the same general type as the actuator disclosed herein, with respect to general construction and operation. Those inventions, however, were directed to mehcanisms for disengaging the motor from the output shaft so that the actuators could be operated by hand. These prior art patents are fully incorporated herein by this reference.